[BUG] Avoid materializing index when list of Series are used to construct DataFrame

[galipremsagar]

Describe the bug
We are materializing RangeIndex when creating a dataframe from list of Series objects.

Steps/Code to reproduce bug

>>> import cudf
>>> s = cudf.Series([1, 2, 3], index=['a', 'b', 'c'])
>>> cudf.DataFrame([s, s, s])
>>> cudf.DataFrame([s, s, s]).index
Int64Index([0, 1, 2], dtype='int64')
>>> import pandas as pd
>>> pd.DataFrame([s.to_pandas(), s.to_pandas(), s.to_pandas()]).index
RangeIndex(start=0, stop=3, step=1)

Expected behavior

>>> cudf.DataFrame([s, s, s]).index
RangeIndex(start=0, stop=3, step=1)

Environment overview (please complete the following information)

• Environment location: [Bare-metal]
• Method of cuDF install: [from source]